1. Field of Invention
This invention is a temperature compensator which is part of a sealed control chamber for a pressure splitter. This compensator can be designed to minimize changes in the gas pressure inside the control chamber caused by gas temperature changes. This temperature compensator is useful when used with a pressure splitter which has its splitting operation affected by pressure or temperature or a combination of temperature and pressure. When used with a pressure splitter affected by temperature and pressure, it enables the pressure and temperature effects on the splitter to be isolated from each other. It is also especially beneficial when it is part of a temperature and pressure responsive pressure splitter used as a carburetor compensator.
2. Description of Prior Art
A commonly used fuel delivery regulator for an internal combustion engine is the carburetor. A carburetor uses a vacuum developed by air movement through a bore (venturi) of a throttle body as a fuel driving force. The carburetor is not entirely self-compensating for changes in atmospheric conditions, and at any specific state of xe2x80x9ctunexe2x80x9d or xe2x80x9cjettingxe2x80x9d, the carburetor""s fuel/air mixture will become richer as air temperature increases and/or air pressure decreases (altitude increases).
Pressure splitters are devices which are connected to a gas or liquid system to provide an intermediate pressure between a higher and a lower pressure. The higher pressure is applied to one port of the splitter, the lower pressure to a second port, and a system of orifices, two or more, xe2x80x9csplitsxe2x80x9d or divides the pressure differential existing between the two ports, establishing an intermediate pressure between the higher and lower pressure. An intermediate port provides access to this intermediate pressure. More details on pressure splitter operation can be found in Applicant""s U.S. Pat. No. 5,879,594 (1999). Pressure splitters can be used to compensate carburetors, adjusting carburetor fuel flow for changes in atmospheric conditions, keeping them properly xe2x80x9cjettedxe2x80x9d, and this application is well known in the art.
Several pressure splitters which are useful as carburetor compensators are shown in U.S. Pat. No. 5,879,594. FIG. 1 of U.S. Pat. No. 5,879,594 shows a pressure splitter having its splitting operation affected only by temperature. This splitter uses a temperature responsive member, or actuator, attached at one end to a body, these two members having different thermal expansion rates. As the temperature of these two members changes, the difference in their lengths changes, affecting the size of an orifice of the splitter, specifically a gap between a head of a screw attached to the actuator and the body. Therefore, the intermediate pressure of the splitter is affected by temperature and the splitter is said to be temperature responsive.
FIG. 2 of U.S. Pat. No. 5,879,594 shows a pressure splitter which has one orifice which changes size with temperature changes as above, and a second orifice which changes size with movement of a sealed bellows. The bellows is affected on one side normally by atmospheric pressure, on the other side by pressure in a sealed control chamber, part of which is the volume inside the bellows. The bellows is shown with an evacuation tube which allows removal of a portion or essentially all of the gas molecules from the bellows. If essentially all of the gas molecules are removed from the bellows/control chamber, the magnitude of the internal pressure change resulting from temperature change will be small because the absolute pressure is small due to the low molecular density. If the bellows/control chamber contains a quantity of gas, the gas pressure internal to the bellows/control chamber will change with a change in the temperature of the gas, thereby affecting the splitter""s operation.
FIG. 3 of U.S. Pat. No. 5,879,594 shows a pressure splitter which only has one orifice which changes size, but it changes size in response to both temperature and pressure. In this splitter the bellows works cooperatively with the lengths and thermal expansion rates of two joined members, an actuator and a body, to affect the size of an orifice of the splitter.
FIG. 6 of U.S. Pat. No. 5,879,594 shows a temperature and pressure responsive pressure splitter as shown in FIG. 3 connected to a carburetor. One side of the pressure splitter is connected to the vacuum existing in the carburetor venturi, the other side is connected to essentially atmospheric pressure, and an intermediate port of the pressure splitter is connected to the carburetor""s float bowl. The splitter xe2x80x9cdividesxe2x80x9d the pressure differential existing between the atmosphere and the venturi, and consequently the intermediate pressure is a vacuum which is a percentage of the carburetor""s venturi vacuum. This percentage depends on the temperature of the splitter""s actuator and on the atmospheric pressure. This intermediate pressure (vacuum) applied to the float bowl reduces the pressure differential which drives the fuel into the venturi and fuel flow is leaned as air temperature increases and/or air pressure decreases (altitude increases), significantly improving engine economy and performance. This pressure splitter and its connection and use with carburetors are well known in the art.
Another form of pressure splitter used as a carburetor compensator is shown in U.S. Pat. No. 5,021,198 to Bostelmann (1991). This pressure splitter is connected to a carburetor similarly to that described above. This pressure splitter has a diaphragm which is exposed on one side to essentially the atmosphere and on the other side to a sealed control chamber containing a quantity of gas. This diaphragm moves in response to the pressures applied to both of its sides, thereby moving a shaped needle. This needle movement changes the relative sizes of the splitter""s orifices, affecting the intermediate pressure of the pressure splitter and hence carburetor fuel flow. Since the control chamber is sealed, it contains a fixed number of gas molecules and the pressure of the gas in the metering chamber changes with temperature. This change in control chamber pressure resulting from temperature change tends to cause a diaphragm movement. A change in atmospheric pressure external to the diaphragm also tends to cause a movement. Hence the intermediate pressure of the pressure splitter is affected by atmospheric pressure and the temperature of the gas in the control chamber, thereby changing carburetor fuel flow (jetting) as a function of atmospheric pressure and control chamber temperature.
It is an object of this invention to provide a temperature compensator for a pressure splitter control chamber which can be used to modify the effect of control chamber temperature changes on control chamber pressure.
It is an object of this invention to provide a temperature compensator for a pressure splitter control chamber which can be specifically designed and constructed so that control chamber temperature changes have minimal effect on control chamber pressure.
It is a further object to provide a temperature compensator for a pressure splitter control chamber which allows the control chamber to be sealed at any specific pressure but any operational temperature with minimal effect on the operation of the pressure splitter.
It is a further object of this invention to provide a temperature compensator for a pressure splitter control chamber used as a carburetor compensator which allows the control chamber to be sealed at any temperature and altitude easily setting the control chamber/pressure splitter for use with carburetors having jetting for different altitudes.